Process of refining glyceride type oils



NOV. 23, 1937. CLAYTON 2,100,276

PROCESS OF REFINING GLYCERIDE TYPE OILS Original Filed July 9, 1935 BURNER THEE/W06 TA 7' H54 TING MEO/ UN 6"? REF/NED 0/4 CENTR/Fl/GE O/L PUMP VA R ABLE JPEED DRIVE EAGE/VT PUMP CRUDE REAGENT STRENGTH OF REAGENT AND CONO/TION-S OTHER 60 I00 //O I50 /40 I50 KO F a TEMPERATURE /N DEGREE)- FAHRENHE/T [/v ws/v TOR BENJAM/N CLA Y TON 5) 6 /o 5 MINOUFTE W M TREA TMNT A 7'7'ORNEK Patented Nov. 23, 1937 UNITED STATES PATENT OFFICE Benjamin Clayton, Houston, '1ex., assignor to Refining, Inc., Reno, Nev., a corporation of Nevada Application July 9, 1935. Serial No. 30,573 Renewed September 20, 1937 13 Claims.

My invention relates to a process of refining a crude glyceride type of oil. A crude glyceride type of oil is one which contains free fatty acids and other impurities. Cottonseed oil in the form in which it is originally recovered from the press is a crude glyceride type of oil. Crude cottonseed oil may contain from 1 to 2%% of free fatty acids. In extremely good years when the seed can be protected from moisture and in exceptional oils, the percentage of free fatty acid in the oil may be less than 1%. Some oils contain more than 2%% but the average 011 may be considered as containing between 1 and 2 of free fatty acids.

Cottonseed and similar oils, fats, and greases are called glyceride type oils since they may be decomposed under certain conditions to form glycerine and free fatty acids, and the term "glyceride type of oil" is used herein in the generic sense to include all oils which may be decomposed to form glycerine and free fatty acids. Such oils are called crude oils when they have not been refined to remove the free fatty acids.

Crude glyceride types of oils are commonly refined by contacting them with a suitable reagent. The word contacting" is used to denote any process in which one material is dispersed in another in the form of fine drops or particles so that the area of contact between the materials is very large. The reagents commonly used are dilute aqueous solutions of an alkali such as caustic soda or caustic potash but the term is used herein to denote any reagent which will unite with the free fatty acids to form foots. The word "foots" is used in the art of refining crude glyceride types of oils to denote the product of the reaction between the reagent and the impurities in the oil. The foots produced by the reaction of a dilute aqueous solution of caustic soda or caustic potash with the free fatty acids of a crude glyceride type oil consist mainly of soap. As a preliminary to efficient contacting it is necessary to thoroughly mix the reagent with the oil to form a dispersion or a mixture in which one material is carried in the form of fine drops in the body of the other. When the oil and reagent are mixed, the neutralization of the free fatty acids to form soap or foots is practically instantaneous but contacting may be continued for a sumcient period and under proper conditions, to cause colored and other impurities to separate with the soap.

Many of the reagents used in the refining of crude glyceride types of oils, while they have a 56. preferential afilnity for the free fatty acids, also tend to react with the oil itself, forming soap and releasing glycerine. The loss in volume of a crude oil during the refining process is called the refining loss". Refining loss is made up partly of the loss due to the formation of foots from the free fatty acids and other impurities initially in the oil, and partly of the loss due to the action of the reagent on the oil itself. The loss due to the reaction of the reagent with the free fatty acids is, of course, necessary as the free fatty acids must be neutralized, and this loss cannot be avoided. The refining loss due to the action of the reagent on the oil itself is to a certain extent unavoidable if complete neutralization of the free fatty acids and reduction of color is to be secured since more reagent, must be used than is theoretically necessary to completely neutralize the free fatty acids, but since the foots produced from the oil itself have a much lower value than the refined oil, any action of the reagent on the oil itself is wasteful and should be avoided. Sufiicient reagent is usually used to not only completely neutralize the free fatty acids, but to also neutralize certain other impurities and give a proper bleach by destroying objectionable color. Any reagent used in excess of the quantity theoretically necessary to completely neutralize the free fatty acids in the oil to be treated is known as excess reagent" or excess caustic". In the refining of crude cottonseed oil containing 1.4% free fatty acid, although only about 0.2% of caustic soda would be theoretically necessary to neutralize the free fatty acid, the refiner, under well established prior practice, would use about 0.54% of caustic soda, or an excess caustic to the amount of 0.34%. If the refiner were using a 14 Baum solution, which contains 9.42% of pure caustic soda, he would use 5.7% by weight of this solution on a crude cottonseed oil containing 1.4% free fatty acid.

It is an object of my invention to provide a process by which the refining loss now suffered in standard methods of refining crude glyceride types of oils may be reduced.

I have found that the refining loss increases very fast as the temperature maintained during contacting is increased. In Fig. 2 I show a graph of the refining loss on a typical oil at various temperatures in a definite fixed time. At 1''. the loss is 24%, but if the dispersion of the same amount of reagent in oil is maintained for the same length of time at F., the loss is 35% or more than four times that experienced at the lower temperature. The refining loss also increases the longer the contacting is continued at a given temperature. This is illustrated in Fig. 3, which shows this increase graphically. At a given temperature the refining loss is 28% if the contacting is continued for five minutes, but if the contacting is continued for fifteen minutes at the same temperature the loss is .82%. It is therefore obvious that to prevent large refining losses it is desirable to conduct the contacting at a low temperature and to accurately control the time of contacting, and it is an object of my invention to provide a process by which both of the objects may be accomplished.

In practice I have found that certain types of cottonseed oil can be successfully refined at temperatures below 110 F. and that if the time of contacting is less than eight minutes, very little of the oil itself will be converted into foots.

The mixture of oil and foots produced by contacting at a low temperature for a short time, although free from fatty acids, contains small quantities of a material which must be removed from the oil before a refined oil can be produced since this material imparts very undesirable qualities to the oil. This material may be called hydrosol and defined as a material which when cold is in gel form and contains foots and water so finely distributed in oil that they appear to be in solution therein. The hydrosol contains a considerable proportion of refined oil and if it is removed with the foots, a considerable amount of refined oil is carried over with the foots, thus increasing the refining loss.

It is a further object of my invention to provide a process in which the oil can be refined at low temperature for a short time, but in which the hydrosol is separated into its constituent parts so that the foots and water may be separated from the refined oil carried in the hydrosol, which refined oil is released to form a part of the desired final product.

I have found that an oil of high purity and good color can be produced if the oil is raised in temperature after the contacting at a low temperature has been carried on a few minutes and while the excess caustic is thoroughly dispersed in the oil. At this higher temperature the action of the excess caustic on the various impurities remaining in the oil is very rapid and complete. The elevated temperature need be maintained for only a very short period to effect results, thus not producing any considerable re fining loss due to the action of the excess caustic on the oil itself.

It is a further object of my invention to provide a process for refining glyceride type oils containing free fatty acids and other impurities, in which the oil is contacted with a suitable reagent to neutralize the free fatty acids, the contacting continued at a low temperature for a sufficient period to react the excess caustic with colored and other impurities and the contacting is further continued for a very short period at a higher temperature, for the purpose of completing the refining.

The process can be applied to the refining of many oils but for the purpose of giving definite figures it will be described as applied to crude cottonseed oil. Crude cottonseed oil contains free fatty acids and other non-fatty impurities such as phosphatides, resins, reducing sugars, and coloring matter. It is an object of the invention not only to neutralize and remove the free fatty acids, but also to remove the nonfatty impurities and improve the color.

A convenient means for practicing my invention is shown on the attached drawing, in which:

Fig. 1 is a schematic diagram showing the apparatus employed, and Figs. 2 and 3 are the graphs previously referred to.

In the apparatus shown in the drawing II is a crude oil tank provided with a heating coil I! by means of which the oil may be heated to a desired degree. It is a reagent tank having a similar heating coil ll. A crude oil pump I! takes oil through a pipe it from the crude oil tank H and delivers it through a pipe H to a mixer II. A reagent pump 20 takes reagent through a pipe 2| from the reagent tank II and delivers it through a pipe 22 to the mixer II. The proportions of the oil and reagent delivered to the mixer it are controlled by a variable speed gear 22 by which the relative speeds of the pumps l and 20 may be regulated so that a properly proportioned mixture fiows from the mixer ll through a pipe 24 to a treating coil 28 in which the excess reagent reacts with colored and other impurities to cause them to agglomerate with the foots.

The pump i5 is driven by a motor 26 and the pump 20 is driven from the motor 26 through the variable speed gear 22.

The treating coil 25, which may also act as a heater, is preferably a coil of pipe so arranged that it forms an elongated tortuous treating zone. The mixture of oil reagent and foots while in this pipe may be heated by the products of combustion from a gas burner 30, the amount of gas delivered to this burner being controlled by a gas valve 3|. The position of the gas valve 2| is controlled by a thermostat 32 which is acted upon by the mixture of oil and foots leaving the reaction zone formed by the pipe 25.

The mixture of oil and foots is then delivered to a pipe 32 having a gauge 34 and a thermometer 3i placed therein. The pipe 33 extends downwardly to a centrifuge 40. The centrifuge 40 may be of any convenient form which is adapted to continuously separate liquids of different specific gravity by centrifugal force. A suitable heating medium such as hot water or steam may be supplied from a pipe to the mixture of oil and foots just as it enters the centrifuge through a valve 4|, or the heating medium may be supplied to the interior of the centrifuge through a pipe I! and valve 45. Refined oil is delivered from the centrifuge 40 through a spout 81 to a pipe 68 and foots are delivered through a spout 68 to a pipe II.

The method of operation is as follows.

I first produce a dispersion of reagent in the crude oil and the resulting mixture is delivered by the pipe 24 to the treating coil 25. This dispersion is produced as follows. The tank H having been filled with crude oil and the tank l3 having been filled with a suitable reagent, the variable speed gear 23 is adjusted to draw from the tanks a suitable proportion of reagent for a definite quantity of oil as pumped. This produces a properly proportioned mixture in the pipe 24. Either or both the oil and reagent may be heated in the tanks I l and II by the heating coils l2 and It so that the mixture in the pipe 24 is at the desired temperature at the time it is delivered to the treating coil 25, or the mixture may be heated in the treating coil. It will probably be found more convenient to heat the mixture in the treating coil 25 by means of the gas burner 30. Some oils require no heating above room temperature but in refining the average cottonseed oil it is desirable to heat the oil during contacting to between 85 F. and 110 F.

I have found that if the dispersion is properly produced, the neutralization of the free fatty acids is nearly instantaneous. The period of actual contacting;.that is, the period during which the reagent in dispersed form is in contact with the oil, may be quite short. The actual time employed should not be longer than that necessary to produce a proper bleach. The length of the contacting time is determined by the speed of the motor I. If the speed of the motor is increased, the velocity of flow through the apparatus is increased and the contacting time is reduced. The proper speed required for the motor 26 may be determined by testing the free fatty acid and color of the oil as it is delivered to the centrifuge l0 and the motor 26 should be run atthe maximum speed at which it is possible to obtain proper bleach. At this speed the refining loss will be quite low.

The mixture delivered through the pipe 33 to the centrifuge 40 contains some hydrosol and at the low temperature at which the mixture is so delivered the hydrosol will not separate into its constituent parts in the centrifuge 40. The foots will also not separate completely from the oil and a high grade refined oil cannot be produced. To overcome this difliculty I very rapidly heat the mixture just before it is delivered to the centrifuge or while it is in the centrifuge. An excellent way to accomplish this heating is to inject hot water or steam from the pipe 42 into the mixture just before it enters the centrifuge. I have found that by such injection the temperature of the foots leaving the centrifuge by the spout 68 may be raised to 160 F. or even higher without material increase in the refining loss. This is, of course, due to the fact that the mixture is in the centrifuge and at this high temperature for a very short time, probably less than one-half a minute. At these higher temperatures the foots and hydrosol are quite liquid. In the centrifuge the foots separate readily and completely from the oil and the hydrosol separates into its constituent parts. The refined oil produced is of good quality and thereflning loss is low.

My process involves producing a dispersion of reagent in the oil to neutralize the free fatty acids; maintaining the dispersion for a suflicient period to insure a substantially complete reaction between the reagent and the other impurities in the oil the contacting being conducted at a temperature sufficiently low and for a sufliciently short time to prevent excessive refining losses; the quick heating of the mixture of oil and the products of the reaction to a temperature at which the hydrosol separates' into its component parts and the foots readily separate from the oil and the relining is completed; and the centrifuging of the heated mixture, the entire time consumed in heating and centrifuging being so short that no considerable refining loss is caused by said heating.

I claim as my invention:

1. A continuous process of refining glyceride type oil which comprises mixing an alkaline reagent with said oil to effect neutralization of the free fatty acids contained in the oil, continuously advancing the mixture through a zone where the heavier constituents are kept in dispersion in the oil and the remaining caustic acts upon the color to produce a proper bleach, maintaining the temperature of the mixture while passing through said zone to a relatively low degree and maintaining the mixture in said zone for a time sumciently short to avoid excessive refining losses during the travel of said mixture but relatively long with respect to the time the mixture is later subjected to an elevated temperature, passing the mixture promptly to a centrifuge while abruptly subjecting it to an elevation of temperature during centrifugal separation.

2. A continuous process of refining glyceride type oil which comprises mixing an alkaline reagent with said oil to effect neutralization of the free fatty acids contained in the oil, continuously advancing the mixture through a zone where the heavier constituents are kept in dispersion in the oil and the remaining caustic acts upon the color to produce a proper bleach, maintaining the temperature of the mixture while passing through said zone to a relatively low degree and maintaining the mixture in said zone for a time sufficiently short to avoid excessive refining losses during the travel of said mixture but relatively long with respect to the time the mixture is later subjected to an elevated temperature, passing the mixture promptly to a centrifuge while abruptly elevating the temperature thereof as it enters the centrifuge.

3. A continuous process of refining glyceride type oils which comprises mixing an alkaline reagent with said oil to neutralize free fatty acids contained in said oil, continuously passing the mixture through a treating zone, maintaining the mixture under relatively low temperature conditions for a period of time sufiiciently short to avoid refining losses while passing through said zone but relatively long with respect to the time the mixture is later subjected to an elevated temperature, whereby to produce a proper bleach without excessive refining losses, abruptly elevating the temperature of the mixture for a relatively short periodv of time while subjecting the mixture to prompt centrifugal separation to remove the resulting sludge and residual solution.

4. A continuous process of refining glyceride type oils which comprises the steps of mixing an alkaline reagent with said oil to neutralize free fatty acids contained in said oil, continuously passing the mixture through a zone of restricted cross sectional dimensions, maintaining the mixture under relatively low temperature conditions for a period of time relatively long with respect to the time the mixture is later subjected to an elevated temperature but sufllciently short to avoid refining losses while passing through said zone, whereby to produce a proper bleach without excessive refining losses, abruptly elevating the temperature of the mixture for a relatively short period of time while subjecting the mixture to prompt centrifugal separation to remove the resulting sludge and residual solution.

5. A continuous process of refining glyceride type oils which comprises mixing an alkaline reagent with said oil to neutralize free fatty acids contained in said oil, thereafter continuously passing the neutralized product through a continuous elongated passageway, maintaining the temperature of the mixture as it passes therethrough at a temperature not in excess of 120 F., and for a considerable period of time but which is sumciently short to avoid excessive refining losses, whereby to effect a proper bleach, promptly subjecting the thus treated product to centrifugal separation while abruptly and quickly elevating the temperature of the oil during said separation, whereby to facilitate the separation of the sludge and residual solution from the refined oil.

6. A continuous process of refining glyceride type oils, contacting free fatty acids by means of an alkaline reagent which comprises: contacting said oil with said reagent by dispersing the reagent in the oil, maintaining the mixture under relatively low temperature conditions for a period of time relatively long with respect to the time the mixture is later subjected to an elevated temperature but suiiiciently short to reduce refining losses, abruptly elevating the temperature of the mixture for a relatively short period of time while subjecting the mixture to prompt centrifugal separation to remove resultant sludge and residual solution.

7. A continuous process of refining glyceride type oil which comprises: mixing an alkaline reagent with said oil to effect neutralization of the free fatty acids contained in the oil, continuously advancing the mixture through a zone where the heavier constituents are kept in dispersion in the oil and the remaining caustic acts upon the color to produce a proper bleach, maintaining the temperature of the mixture while passing through said zone to a relatively low degree and maintaining the mixture in said zone for a time relatively long with respect to the time it is later subjected to an elevated temperature but suificiently short to avoid excessive refining losses during the travel of said mixture, passing the mixture promptly to a centrifuge while abruptly subjecting it to an elevation of temperature during centrifugal separation by admixture therewith of a heated fluid.

8. A continuous process of refining glyceride type oil which comprises: mixing an alkaline reagent with said oil to effect neutralization of the free fatty acids contained in the oil, continuously and rapidly advancing the mixture through a zone where the heavier constituents are kept in dispersion in the oil, maintaining the temperature of the mixture while passing through said zone at a relatively low temperature and for a sumciently short time to avoid excessive refining losses during the travel of said mixture, passing the mixture promptly to a centrifuge while abruptly subjecting it to an elevation of temperature during centrifugal separation.

9. A continuous process of refining glyceride type oils which comprises: mixing, at a relatively low temperature, an alkaline reagent with said oil to effect neutralization of the free fatty acids, maintaining the resulting mixture-mt the relatively low temperature for a time sufficient to D O- duce a proper bleach without excessive refining losses, abruptly subjecting the mixture to an elevation of temperature while subjecting it to centrifugal separation.

10. A continuous process of refining glyceride type oils which comprises: mixing an alkaline reagent with said oil at a relatively low temperature whereby to disperse the reagent in the oil, maintaining the resulting mixture at the relatively low temperature for a time sufiicient to pro duce a proper bleach without excessive refining losses, subjecting the resulting mixture to centrifugai separation while abruptly raising the temperature thereof, whereby to condition it for the separation of the resulting soap stock from the refined oil.

11. A continuous process of refining glyceride type oils which comprises the steps of mixing the oils with an alkaline reagent at a relatively low temperature for a time sufiicient to produce a proper bleach without excessive refining losses and introducing the resulting mixture to a centrifuge, conditioning the mixture for centrifugal separation of the foots and the refined oil by sharply elevating the temperature of the mixture during centrifugal separation.

12. The process as defined in claim 11 in which the temperature is elevated by introducing a heated iiuid into the centrifugal separator for admixture with the mixture.

13. A continuous process of refining glyceride oils which comprises the steps of admixing an alkaline reagent with the oil at a relatively low temperature to form a difiicultly separable emulsion, maintaining the resulting mixture at the relatively low temperature for a time sufiicient to produce a proper bleach without excessive reiin ing losses, subjecting the mixture to the action of centrifugal separation and facilitating such separation by applying heat to the mixture while in the separator whereby to break the emulsion and separately discharging the foots and refined oils from the separator.

BENJAMIN CLAYTON. 

